/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001, 2002,2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xerces.internal.util;


/**
 * This class is an unsynchronized hash table primary used for String
 * to Object mapping.
 * <p>
 * The hash code uses the same algorithm as SymbolTable class.
 *
 * @author Elena Litani
 * @version $Id: SymbolHash.java,v 1.7 2010-11-01 04:40:14 joehw Exp $
 */
public class SymbolHash {

  //
  // Constants
  //

  /**
   * Default table size.
   */
  protected int fTableSize = 101;

  //
  // Data
  //

  /**
   * Buckets.
   */
  protected Entry[] fBuckets;

  /**
   * Number of elements.
   */
  protected int fNum = 0;

  //
  // Constructors
  //

  /**
   * Constructs a key table with the default size.
   */
  public SymbolHash() {
    fBuckets = new Entry[fTableSize];
  }

  /**
   * Constructs a key table with a given size.
   *
   * @param size the size of the key table.
   */
  public SymbolHash(int size) {
    fTableSize = size;
    fBuckets = new Entry[fTableSize];
  }

  //
  // Public methods
  //

  /**
   * Adds the key/value mapping to the key table. If the key already exists,
   * the previous value associated with this key is overwritten by the new
   * value.
   */
  public void put(Object key, Object value) {
    int bucket = (key.hashCode() & 0x7FFFFFFF) % fTableSize;
    Entry entry = search(key, bucket);

    // replace old value
    if (entry != null) {
      entry.value = value;
    }
    // create new entry
    else {
      entry = new Entry(key, value, fBuckets[bucket]);
      fBuckets[bucket] = entry;
      fNum++;
    }
  }

  /**
   * Get the value associated with the given key.
   *
   * @return the value associated with the given key.
   */
  public Object get(Object key) {
    int bucket = (key.hashCode() & 0x7FFFFFFF) % fTableSize;
    Entry entry = search(key, bucket);
    if (entry != null) {
      return entry.value;
    }
    return null;
  }

  /**
   * Get the number of key/value pairs stored in this table.
   *
   * @return the number of key/value pairs stored in this table.
   */
  public int getLength() {
    return fNum;
  }

  /**
   * Add all values to the given array. The array must have enough entry.
   *
   * @param elements the array to store the elements
   * @param from where to start store element in the array
   * @return number of elements copied to the array
   */
  public int getValues(Object[] elements, int from) {
    for (int i = 0, j = 0; i < fTableSize && j < fNum; i++) {
      for (Entry entry = fBuckets[i]; entry != null; entry = entry.next) {
        elements[from + j] = entry.value;
        j++;
      }
    }
    return fNum;
  }

  /**
   * Return key/value pairs of all entries in the map
   */
  public Object[] getEntries() {
    Object[] entries = new Object[fNum << 1];
    for (int i = 0, j = 0; i < fTableSize && j < fNum << 1; i++) {
      for (Entry entry = fBuckets[i]; entry != null; entry = entry.next) {
        entries[j] = entry.key;
        entries[++j] = entry.value;
        j++;
      }
    }
    return entries;
  }

  /**
   * Make a clone of this object.
   */
  public SymbolHash makeClone() {
    SymbolHash newTable = new SymbolHash(fTableSize);
    newTable.fNum = fNum;
    for (int i = 0; i < fTableSize; i++) {
      if (fBuckets[i] != null) {
        newTable.fBuckets[i] = fBuckets[i].makeClone();
      }
    }
    return newTable;
  }

  /**
   * Remove all key/value assocaition. This tries to save a bit of GC'ing
   * by at least keeping the fBuckets array around.
   */
  public void clear() {
    for (int i = 0; i < fTableSize; i++) {
      fBuckets[i] = null;
    }
    fNum = 0;
  } // clear():  void

  protected Entry search(Object key, int bucket) {
    // search for identical key
    for (Entry entry = fBuckets[bucket]; entry != null; entry = entry.next) {
      if (key.equals(entry.key)) {
        return entry;
      }
    }
    return null;
  }

  //
  // Classes
  //

  /**
   * This class is a key table entry. Each entry acts as a node
   * in a linked list.
   */
  protected static final class Entry {

    // key/value
    public Object key;
    public Object value;
    /**
     * The next entry.
     */
    public Entry next;

    public Entry() {
      key = null;
      value = null;
      next = null;
    }

    public Entry(Object key, Object value, Entry next) {
      this.key = key;
      this.value = value;
      this.next = next;
    }

    public Entry makeClone() {
      Entry entry = new Entry();
      entry.key = key;
      entry.value = value;
      if (next != null) {
        entry.next = next.makeClone();
      }
      return entry;
    }
  } // entry

} // class SymbolHash
